1. Field of the Invention
The invention relates to baseline wandering correction devices and methods.
2. Description of the Related Art
In wireless communication systems, the baseline wandering problem for receivers results in the receiving of wrong signals and inoperativeness of the wireless communication system. As such, correcting the baseline wandering problem has always been an important topic for the wireless communication system industry.
For Bluetooth communication systems, signals are modulated by a Gaussian Frequency Shifting Keying module (GFSK module). Comprised of RX IF filtering and demodulator inter symbol interference (demodulator ISI), a filter transient response or local oscillator frequency of the transmitter and the receiver both cause baseline wandering.
One conventional technique to solve baseline wandering is specific coding, such as Return to zero (RZ) code or Manchester code, in which the data stream does not contain a direct current component, thus reducing baseline wandering. The conventional technique, however, also reduces baseband width of the system and does not perform well when applied in Bluetooth systems.
Another conventional technique for solving baseline wandering is the Alternating Current coupling (AC coupling) method, in which signals are AC coupled to a following circuit stage. The AC coupled signals at the following circuit stage restore a DC voltage level thereof to reduce baseline wandering. The AC coupling method, however, is impracticable when there are DC components in the signals as the validity period for applying the AC coupling method is restricted.